To solve this problem, there's an intermediate class that imports the correct set of methods. This class then inherits from the intermediate class. This works, and isolates the tricky bits to a single intermediate class, but it also demonstrates the problems that can crop up when multiple inheritance is combined with a strong aversion to code duplication.

Inheritance shenanigans aside, this class is a good example of a compound field that includes other compound fields and also provides an "inflated" internal value (a DateTime object). This is the most complex custom field example in this distribution. It does everything: nested compound fields, validation, inflate/deflate, and coalesce/decompose.